In-Operando Photovoltage and Photomotion Scanning Probe Microscopy on Optoelectronic Devices

Optoelectronic devices, such as solar cells and light-emitting diodes, are essential to our modern high-tech and sustainable society. While high-performance devices are widely available, the growing demand necessitates further improvements in efficiency and the replacement of scarce materials. Achieving these advancements requires a deep understanding of the nanoscale processes that influence device performance.
Scanning probe microscopy is a powerful technique that can elucidate how nanoscopic processes affect macroscopic device properties. In the context of optoelectronic devices, light-driven in-operando scanning probe microscopy, specifically Kelvin probe force microscopy, can identify charge carrier transport barriers and the origins of photovoltage [1, 2], thereby offering valuable insights into device physics [3-5].
This presentation will showcase several examples across various devices, including organic solar cells, light-emitting diodes [5], and two-dimensional materials. Emphasis will be placed on different scanning modes, their advantages, and the key findings derived from these techniques. Additionally, the presentation will cover time-dependent Kelvin probe and atomic force microscopy measurements [6] to analyze material systems exhibiting light-induced mechanical displacement (photomotion) [7].

1 Saive, R.: ‘Investigation of the Potential Distribution within Organic Solar Cells by Scanning Kelvin Probe Microscopy’, 2014
2 Saive, R., Scherer, M., Mueller, C., Daume, D., Schinke, J., Kroeger, M., and Kowalsky, W.: ‘Imaging the electric potential within organic solar cells’, Advanced Functional Materials, 2013, 23, (47), pp. 5854-5860
3 Saive, R.: ‘S-Shaped Current–Voltage Characteristics in Solar Cells: A Review’, IEEE Journal of Photovoltaics, 2019
4 Saive, R., Mueller, C., Schinke, J., Lovrincic, R., and Kowalsky, W.: ‘Understanding S-shaped current-voltage characteristics of organic solar cells: Direct measurement of potential distributions by scanning Kelvin probe’, Applied Physics Letters, 2013, 103, (24)
5 Weigel, C.S., Kowalsky, W., and Saive, R.: ‘Direct observation of the potential distribution within organic light emitting diodes under operation’, physica status solidi (RRL)-Rapid Research Letters, 2015, 9, (8), pp. 475-479
6 Eftekhari, Z., Rezaei, N., Stokkel, H., Zheng, J.-Y., Cerreta, A., Hermes, I., Nguyen, M., Rijnders, G., and Saive, R.: ‘Spatial mapping of photovoltage and light-induced displacement of on-chip coupled piezo/photodiodes by Kelvin probe force microscopy under modulated illumination’, Beilstein journal of nanotechnology, 2023, 14, (1), pp. 1059-1067
7 Luiten, W.M., Van Der Werf, V.M., Raza, N., and Saive, R.: ‘Investigation of the dynamic properties of on-chip coupled piezo/photodiodes by time-resolved atomic force and Kelvin probe microscopy’, AIP advances, 2020, 10, (10), pp. 105121